glVertexAttribFormat, glVertexAttribIFormat and glVertexAttribLFormat specify the organization of data in vertex arrays. attribindex specifies the index of the generic vertex attribute array whose data layout is being described, and must be less than the value of GL_MAX_VERTEX_ATTRIBS.

size determines the number of components per vertex are allocated to the specifed attribute and must be 1, 2, 3 or 4. type indicates the type of the data. If type is one of GL_BYTE, GL_SHORT, GL_INT, GL_FIXED, GL_FLOAT, GL_HALF_FLOAT, and GL_DOUBLE indicate types GLbyte, GLshort, GLint, GLfixed, GLfloat, GLhalf, and GLdouble, respectively; the values GL_UNSIGNED_BYTE, GL_UNSIGNED_SHORT, and GL_UNSIGNED_INT indicate types GLubyte, GLushort, and GLuint, respectively; the values GL_INT_2_10_10_10_REV and GL_UNSIGNED_INT_2_10_10_10_REV indicating respectively four signed or unsigned elements packed into a single GLuint; and the value GL_UNSIGNED_INT_10F_11F_11F_REV indicating three floating point values packed into a single GLuint.

glVertexAttribLFormat is used to specify layout for data associated with a generic attribute variable declared as 64-bit double precision components. For glVertexAttribLFormat, type must be GL_DOUBLE. In contrast to glVertexAttribFormat, which will cause data declared as GL_DOUBLE to be converted to 32-bit representation, glVertexAttribLFormat causes such data to be left in its natural, 64-bit representation.

For glVertexAttribFormat, if normalized is GL_TRUE, then integer data is normalized to the range [-1, 1] or [0, 1] if it is signed or unsigned, respectively. If noramlized is GL_FALSE then integer data is directly converted to floating point.

relativeoffset is the offset, measured in basic machine units of the first element relative to the start of the vertex buffer binding this attribute fetches from.

glVertexAttribFormat should be used to describe vertex attribute layout for floating-point vertex attributes, glVertexAttribIFormat should be used to describe vertex attribute layout for integer vertex attribute and glVertexAttribLFormat should be used to describe the layout for 64-bit vertex attributes. Data for an array specified by glVertexAttribIFormat will always be left as integer values; such data are referred to as pure integers.